OK, so crown race on new fork, new fork on bike.

Re-attach old cantilever brakes, line pad up with rim, check return action and … pop, the spring on the left hand fork has popped out of the little hole on the tab next to the brake stud that fork it goes in.

Try again, same thing. And again. Don’t want to keep trying because every time it pops out the spring scratches the tab with he hole in.

The forks are Surly Big Dummies. Brakes are old Shimano Acera x (c.1997) which worked fine on the previous forks and work fine on the back. They weren’t used much despite their age, before I got the bike. There is only one hole for the spring, not the traditional 3. The single hole is the ‘middle’ position if there were 3.

Basically, with the brake arm on the brake stud and the allen bolt fully tightened to hold it on, the bit of the spring that sticks out to go in the hole spring isn’t long enough to stay in there.

The other side is fine – I notice that bits that stick out of the spring to go into the holes on the left hand arm are shorter than the spring on the right, and the springs are seemingly a different colour – the longer one on the right is more a gold colour, while the shorter left hand one is silver.

This is the same on the back brake – one shorter than the other – though that’s never been a problem.

What to do!?

Tempted to buy an Avid Shorty / similar, but would like to keep re-using the old components as much as possible – that’s kind of the point of this particular bike.

Cheers!

Sb

Have you got the springs in the wrong way round? When I last had cantis (1996?!), one end (the sticky out bit) of the spring was longer than the other. The longer bit normally goes into the middle hole on the fork boss.

Is the brake sitting fully on the canti stud, or is it binding somehow leaving it not flush? Is there any play on the brake with the bolt done up tight? left and right springs are often a different colour so you know which is which.

Bigyinn – no – the ‘sticky out bit’ on the spring is the same length whichever way round it is.

Stevet1 – It’s not binding, but I have noticed that even when fully screwed in, the allen bolt does not ‘press’ the brake arm towards the fork leg. i.e the brake stud seems a bit long so the allen bolt can’t tighten any further onto the brake arm. Some sort of washer might work to apply greater pressure to the arm to push it harder against the fork?

so there is play in the canti arm i.e. you can slide it along the canti stud even when the bolt is fully tightened up? Is the canti stud fully inserted in the fork? If so, then I think I’d be swapping the brake arms around just to see if the other arm would tighten up. It obviously will be facing the wrong way etc. but you just need to test if its the canti brake or the brake stud which is out of tolerance.

Hmmm. Tried swapping round arms on the studs, as well as the springs in the arms, to test this – both arms go onto the stud the same amount – the only thing that makes it pop out on either side is the spring being too short…

I wonder if the original owner (2nd hand bike) replaced the left hand side spring on both front and back, with a shorter one?

I just examined the innards of a similar-era Altus brake from my gf’s old bike (slightly lower end but similar brake) and it has different – coloured springs too – one gold, one silver, but these are the same length as each other (incidentally, they’re the same length as the shorter one of mine which pops out, so I can’t steal one!)

Makes me think that the springs should be the same length as each other…

Did the old fork have pre-2008 studs in? Maybe compare the stud lengths.

Jumble – the old forks were 1997! New studs are about 1.5mm longer in terms of the whole stud, including the thicker part, but the same along the thinner part…

Is this a common thing / incompatible standards?